Method for purifying rosin



Patented July 17, 1951 'U'NIT E D STATESv PATENT OFFICE METHODcFOR PURJIFSEING ROSIN 'William G. Knox and GeorgeL. Deniston, Dayton, Ohio, assignors, by mesne assignments, to

Howard M. I-Iempstead and Louise M. Hempstead, both of Mobile, Ala.

. No Drawing. Application Ju l y.5,,1349, Serial No. 103,174

'14 Claims. I

This invention relates to amethod of treating rosin. More particularly it relates to thepurification of rosin by extractive methods.

Still more "particularly it;-re1ates to a' method for removing .dark zcolored: material from wood rosin to lightenits color.

'Rosins of the trade Pare 'judged for purity by the lightness :of their @color. Those having clear bleached-straw color :are called WW or water white rosins' -and :command a 1 premium price.

Near the 'bottom' of. the-rating scale are the FF" and "G rosins which are dark and blackbrown in color. Theseiidark coloredrosins constitute a large :percentager-of. the rosin yield from present manufacturing procedures.

In=order to obtai-nrhigher yields ofpremium grade "-rosins,-th.e-.'crude -rosins= ha-ve been subjected'to such treatments as precipitation f a portion of. the rosin -by'the'use of strong acids and-alkalis,' absorption of :color bodies by diatomaceous earth, activated :charcoal'a-nd the like, vacuum distillation, liquid phase extraction. orxby a combination -of various :of thexabove methods.

All of the :above mentioned-methods -have:-ob-

extraction of rosins with liquid agents, but has met with indifferent success, and. as'far'aswe know has received only limited acceptance :in the'industry, because of the cost of reagents, such as furfural *and "methyl carbitol and the heavy losses of these'reagents. I

In these processes after thecolorbody solvent has extracteda portion of the'colorbodiesfrom the naptha solution of rosin-the solvent 'solution is removed to recoveringunitswhere the solvent is separated and recovered *by 'disti'llation.

Due to inability to remove all of the solvent from "the residue, large losses of solvent with consequent heavy operating costs are incurred. The losses when attempting to utilize methyl carbitol, which boils atabout 380 -F.,have been such as toclass thisprocess out'ofthec ompetitive market.

It is the primary object "of this "invention, therefore, to provide a. process for the-purification "of wood rosin which overcomes {the' *'disadvantages of processes utilized heretofore vide a process capable of producing a greater color improvement in wood rosins than hasbeen evidenced heretofore.

Another object of this invention is to provide a process wherein the steps are adaptable to batch or continuous operation.

A still further object of this invention is tc provide a process wherein the more expensive reagentsaremerely transfer-agents and as such recoverable for recycling through the various process steps without appreciable loss.

It'is another object of'this invention to provide a process in which the operating costs are reduced becauseofthe smaller volume of liquids which may berecycled in the various process steps.

Inaccordance with 'a process disclosed in the co-pending application of Cunningham and Knox, {Serial No. 94,852, filed May 23, 1949, there is formed and separated several combinations of miscible solvents which are separable into homogeneous solution-phases fromjwhich product and solvent are relatively completely separated and "recovered.

By this process a major portion of the rosin product is recovered as upgraded higher value rosin and a minor portion-of the rosin is re-" covered'as dark low grade-rosin.

Advantage is taken in this process of the discovery-that,for example, diethylene glycol monomethyl ether has limited solubility'in naphtha, whereas naphtha is slightly soluble in the ether, and in combination therewith makes an elffectivemedium"foraccumulation of soluble color bodies.

The processissimplified by the discovery that the naphtha and color-bodies are rendered insoluble in the ether solution diluted with water.

In brief, -the process is carried out by preparing a solution ofrosin in'a primary solvent andextractingthe primary'solvent solution with a"secondary -solvent' in which the primary solvent has limited solubility, to form a two phase system in which the mixed solvent phase preferentially-dissolves the color bodies, effecting phase separation between primary and secondary solvent solutions by diluting the mixed solvent phase with-an agent-.misciblewiththe secondary solvent and relatively completely recovering the various components of the segregated solution by'--'distillation.

springing agents utility depends upon the come pleteness with which the agent removes second ary solvent from the phase in which it is found. When utilizing alcohol ethers, alcohols and the like as secondary solvents, water serves as an inexpensive and efficient agent.

Inasmuch as the springing agent is merely recycled complete separation from the solvent is unnecessary. It is preferred, however, to choose springing agents which are separable into a re cycle stream containing lessthan 5 percent of solvent.

Our modification of this process is based upon the discovery that by carrying out the extraction part of the process under the hereinafter described conditions, the performance of this system may be altered to such an extent that not only can the quantity of solvent which must be recirculated be markedly reduced, but a more complete removal of color bodies can be effected, so that a higher. rating for rosin can be produced. A

The ecorfirfy of an extraction system naturally depends upon the relative quantities of solvents which must be circulated. In our improved system the first extraction step :is carried out as follows: p p I The solution of rosin in primary solvent is mixed with secondary solvent. The mixture is warmed to a point where a homogeneous mixture is formed. The solution generally is heated to a temperature in the range of 85 F. to 150 F., and preferably to a temperature in the range of 90 F. to 110 F. I

After agitation for about 15 minutes the solution is cooled to a temperature in the range of 0 to 65 F., although temperatures slightly outside this range may be utilized without lowering the efliciency of the system to too great an extent. For economic reasons it is preferred to op-.

crate the extraction step at about 45 F. to 60 F., and particularly at about 50F.

The concentration of rosin in the primary.sol-. vent solution fed to the extraction stream is limited to between .5- and 30 percent by weight of rosin,- preferably in the range of 10 to per cent. 7 we The concentration of color bodies is generally limited to a maximum of about 20 percentby weight in the mixed solvent phase. tions below 10 percent are considered poor operation in treating acrude rosin.

If, however, the process is carried out by repeated extractions, naturally the concentration of color bodies afterthe first extraction would not reach 10 percent with'any appreciable circulation of secondary solvent, and therefore the invention is not tied to a lower limit.

For each volume of primary solvent and rosin fed to the extracting system, in our modified Concentra- -v process, we circulate about one-twelfth to one This: solvent ratio, however, may be varied somewhat sixth of a volume of secondary solvent.

depending upon the contamination of the rosin.

In the solvent springing step we have found the separation of phases and transfer of color bodies to be more complete and efficiently performed when the step is carried out in a temperature in the range of 45 F. to 65 F. and preferably at a temperature of about 50 F., although temperatures outside the above range do not alter the separation efficiency as markedly as rise in temperature affects the efficiency of the extraction step.

In this cold water washing step the volume of water required is such that about one-fourth to one-half volume of springing agent is required for each volume of ether solvent solution.

The method of operation will be more clearly understood from the description in ,the following examples:

Example I A batch of FF rosin, for example, weighing 1000 grams may be dissolved in about 5000 cc. of

a mixture of pentane and hexane. Thissolution may be thoroughly mixed with 600 cc. of diethylene glycol mono ethyl ether, fed to the mixing chamber at a temperature of about 150 F; The

temperature after mixing will be about 100 F.

for the whole batch. The mixture may then be cooled by passing brine through cooling coils in the mixing vat until the temperature of the mixture is reduced to about 50 F.

The light colored rosin mixture may be segregated as a light colored solution and distilled at about F. to recover the pentane solvent.

The dark colored solution may be mixed with approximately 400 cc. of water. After allowing the solutions to settle, thissolution divides into a second pentane rosin solvent solution of about 300 cc. volume, containing substantially all of the color bodies.

The pentane solvent may be distilled from this solution at about 150 F. A volume of about 1000 cc. of alcohol-water solution is recovered and rectified at a temperature of about 212 F. to drive off the water which is condensed and reused in the water wash or springing step.

Example II A.v solution of FF rosin, .for example, having a ratio of one gram of rosin for each 5 cc. of solvent naphtha may be continuously processed as follows:

The solution may be continuously mixed with one volume of tetrahydrofurfuryl alcohol for each six volumes of naphtha solution.

, The mixture may be heated to approximately 110, F. and run through suitable reaction timing equipment to allow,a reaction time of approximatelyf15 minutes. H

The homogeneous stream of solution issuing from' the timing equipment may then be introducedinto phase separation equipment wherein the solution is cooled to approximately 45 F.

From the top of this-equipment there is continuously removed a clear rosin rich naphtha solution, and from the bottom of this equipment is continuously removed a dark alcohol rich solution.

The efiluent top stream of light colored naphtha solution may be distilled at approximately F. torecover the naphtha and light colored rosin separately. l

phaseto produoe'immiscible phasesthereimrsegregating 'theuiimmisciblevphases; andiheatingeeafch segregated solution to: recover.thezindividuallliquids for reuseinthe process.

4. Themethodof-removing colori bodiesrtfrom a solution: of. low: grade rosin:=:which s'compr-ises, mixing a: solutionof rosin :in 1 a 'waterrimmiscible primaryaisolvent with ar seoondary waterzmiscible solvent rhaving solventapower for- 'the. colorvbodies,

agitating and warming-:themixturezuntil:ahomogeneous solution. is formed;'coolingrsaichsolution to produce two separate solutionrphases,x'segregatinggrsaidr phases, .cspringingsisecondary solvent from each phaseby'sxadditionx ofcwater thereto,

segregating a: pale rosini..solution,;a '.dark'rros'in solution, and-a springing:agente'secondaryrsolvent Tempera- Extrac-- -Vo1ume -Rosm "ture at I Starting v 7 tion Step ,Ratiom Process Material $32 5 Tempera- 2 33; extraction I ture n rstep I IF J Counter-current 1--FF-Ros1n. 73 73 l 0.25 Batch L 100 50 l 0.15 Oountercurrent FF Rosin; N; l -100 50 1 0.10

It :will be understood that whilethere have. been givenherein-certain specific examplesof'thepractice of .this invention,- it is not.intended thereby to have. this invention limited to. or circumscribed by the: specifiodetails .of. materials, proportions, ortconditions'herein, specified, in viewof the, fact thatthisinvention may be. modifiedeaccording to individual.preferencaonconditions.without necessarily departing from the spirit of thisdisclosure and therscopeoflthe appended claims.

I ..We.claim:. 1 .1. The method. of removing 'oolori-bodies .from solutions of low. graderosin .Which .comprises,.mi-X ing a solution of.rosin inauaterimmiscible primary solvent with. a secondary water..miscible solvent having. solventpower.for-the .colorbodies to form a homogeneous. solution, segregating ..a primary solvent rich. phase .and a secondary. solvent-rich phase,- springing saidsecondary solvent from-each phase .by. .additi0n ...of watei-Z.-theret.0, segregating a pale, rosinsolution, .a...dark rosin solutioneand aspringingagent-secondary. solvent solution,v and recovering. thes'olventsgand. springingagent for reuseinthesystem.

2..The method. of, removing. colonbod-ies froma solution, of low. grade rosin-lwhich'. comprises, ,mixing a solution. oirosin in. a..-w.ater immiscible primary so1vent..with.a secondary water miscible solvent having solventpowen for color bodies .to forma homogeneous solutionleifectingphase separation by. cooling-saidsiolution, separating secondaryus'olventffroml eachsphase by addition of Water thereto,.segregatihg two separate rosin solutions and a secondary solvent-springing agent solution, and recovering the individual liquids for reuse in the system. p

3. The -method ofrem'ovingfcolor bo'diesffrom a solution of low grade rosin which comprises, mixing a solution of rosinl-in auwater immiscible primary-solvent with a secondary water miscible solvent having solvent power for the color bodies to. form-ahomogeneous solution, coolingatheimixture tdeiT-ect separation of a pale ros-i-n phase andya secondary solvent rich phase, spring-in the contaminated quantity of secondary solvent from the pale phase by addition of Water to said phase, segregating a pale rosin-primary solvent solution from the springing agent-secondary solvent solution, mixing water with the secondary solvent rich solution, and separately. recovering the .solvents and. springing agent for reuseinthe system.

-;5. The method of. removing. color. :bodies from a solution of .lowgrade rosin .whichncomprises, mixing a.solution of rosin in..a water.immiscible primary solvent with a, secondary-water miscible solventhaving sol-vent powerlfor the colon-bodies, agitatingv and warming the-mixture. to -attemperature in the range of.85:F..to. l.50iF.: whereby a homogeneoussolution. formed, .cooling .said solution to produce two rseparate. solution. phases, segregating said phases, springingsecondarysolvent from each phase .byaddition ofwatenthere- 40 to, segregatingapale rosin solution, adarkrosin solution, and a springing .agentesecondary-solvent solutionyland. separately recovering the solvents anduspringing. agent-tor reuse. inthesystem.

6-. Themethod of' removing color bodies from 5 atsolution of -.low...grade rosin -.wh-ichcompr-ises,

mixing a warm solution of rosin in.;a wat.er'-immiscible .pri-mary-solvent -=with .-a= warm-secondary Water misciblesolvent havingsolvent .powerfor the. color bodies... agitating the 1- mixture- .suntil .a homogeneous solution. is formed, cooling .--said solutionto produce twoseparate solution phases, segregating saidphases, spring-ingsecondary solvent for. veachphase. by additionof-water-.-thereto, segregating a pale rosin solution, .adark, rosin solution -,-and=a springing.agentsecondary sol-vent solution. and separately recovering .-the--,'solv.ents and springing agent for reuse in thesystem.

-7. The :methodof. removing color bodies from a solution;of .low grade .rosinwhich. comprises; mix- 0 ing. atsolutionr of rosin; in a water immiscible primary solventswith .a. secondary water. miscible solvent .having', solvent power. .for the. colorlbodies, agitating and Warming :the mixturertma [temperaturesinstherrange of. 90 to\1-1-O:'F.-!whereby a v homogeneous solution. is formed; pooling-said solution to producertwolseparatesolution-phases, segregating said; phases springing-2'secondaryesol- Vent gfor. eachsphase. .byaaddition-.-of.-vvater.- thereto, segregating a palewrosinasolution, a dark rosinsolution, and aspringing.agentesecond ryrsolvent solutiomandwseparately recovering rhessolvents and springing agent for reuse in the system.

8. The method of removing color bodies from solutions of low grade rosin which comprises, mix- 5 ing a solution of rosin in a water immiscible primary solventwith a secondary water miscible solvent havingsolvent power for the color bodies to form ahomogeneous solution, cooling said homogeneous solution to :a temperature in the range of F. to 65 F., segregating a primary solvent rich phase and a secondary solvent rich phase, springing said secondary solvent from each phase by addition of water, segregating a pale rosin solution, a dark rosin solution and a springing agent-secondary solvent solution, and recoveringvthe solvents and springing agent for reuse in the system. i

T9. The method of removing color'bodies from solutions of low grade rosin which comprises, mixing-lai'solution of rosin in a water immiscible primary solvent with a secondary water miscible solvent having solvent power for the color bodies to form a homogeneous solution, cooling said homogeneous solution to a temperature in the solvent rich phase and a secondary solvent rich phase, springing said secondary solvent from each phase by addition of water thereto, segregating a effect separation oftwo distinct'solution phases, segregating the light colored phase from the dark colored phase, mixing water'with the light colored phase, segregating a tetrahydrofurfuryl alcohol free pale rosin solution, mixing water with the dark phase, segregating'a dark rosin solution and a water-tetrahydrofurfurylalcohol solution, dis tilling the naphtha solution from the rosin solutions to recover a light and a dark rosin-and naphtha, and rectifying the tetrahydrofurfuryl alcohol solution to recover separately the alcohol and water components for recycling in the system.

13. The methodof removing color bodies from a solution of low grade rosin-which comprises, dissolving one unit weight of rosin in five unit volumes of a mixture of pentane and hexane, mixing the solution with one volume of diethylene glycol monoethyl ether for each six volumes of solution, agitating and warming the mixture to a temperature of about 100 F., cooling the sopale rosin solution, a dark rosin solution, and a springing agent-secondary solvent solution, and recovering the solvents and springing agent for reuse in the system. -10. The method of removing color'bodies from a solution of low grade rosin which comprises, mixing a solution of rosin in a water immiscible primary solvent with a secondary Water miscible solvent having solvent power for the color bodies, agitating and warming the mixture to a temperature in the range of85 F. to 150 F. until a homogeneous solution is formed, cooling said solution to a temperature in the range of 0 to 65 F. to produce two separate'solution phases, segregating s'aid 'phases, springing secondary solvent from each phase by addition of water thereto, segregating a pale rosin solution, a dark rosin solution, and a springing agent-secondary solvent solution,- and separately recovering the solvents and springing agent for reuse in the'system.

11. The method of removing color bodies from a solution of low grade rosin, which comprises dissolving the rosin in a mixture 01 pentane and hexane, mixing the solution with diethylene glycol monoethyl ether, agitating and warming the mixture to a temperature in the range of 85 F. to 150 'F. until a homogeneous solution is formed, cooling said solution to a temperature in the rangeof 0 to 65 F. to effect separation of two distinct solution phases, segregating the light colored phase from the dark colored phase, mixing water with the light colored phase, segregating a diethylene glycol monoethyl ether-free pale rosin solution, mixing water with the dark phase, segregating a dark rosin solution and a waterdiethylene glycol monoethyl ether solution, distilling the pentane-hexane solvent from the rosin solutions to recover a light and a dark rosin, and rectifying the diethylene glycol monoethyl ether solution to recover separately the ether and water components for recycling in the system.

12. The method of removing color bodies from a solution of low grade rosin, which comprises dissolving the rosin in a solvent naphtha, mixing the solution with tetrahydrofurfuryl alcohol, agitating and. warming the mixture to a temperature in the range of 85 F. to 150 F. until a homogeneous solution is formed, cooling said solution to a temperature in the range of 0 to 65 F. to

lution to a temperature of about 50 F. to effect separation of two distinct solution phases, segregating the light colored phase from the dark colored phase, mixingwater with the light colored phase, segregating a diethylene glycol monoethyl ether-free pale rosin solution, mixing one volume of water with each volumeof dark phase solution, segregating a dark rosin solution and a water-diethylene glycol monoethyl ether solution, distilling the pentane-hexane solvent from each of the rosin solutions to recover a light and a dark rosin, and rectifying the diethylene glycol monoethyl ether solution to recover separately the ether and water components for recycling in the system. 7 i,

14. The method of removing color bodies from a solution Of low grade rosin which comprises, dissolving one unit weight of rosin in five unit volumes of solvent naphtha, mixing the solution with one' volume of'tetrahydrofurfuryl al cohol for each six volumes of solution, agitating and warming the mixture'to a temperature or approximately 110 1 K, cooling the solution to a temperature of approximately 45 F. to effect sep-:

aration of two distinct solution phases, segregating the light coloredphase from the dark colored phase, mixing water with the light colored phase, segregating a tetrahydrofurfuryl alcohol f ree pale rosin solutionylrtrixingbne volume of water. with two volumes of alcohol solution, segregating a dark rosin solution anda water-tetrahy drofurfuryl solution, distilling the naphtha so-. lution from each of the rosin' solutions to recover a light and a dark rosin, and rectifying the tetrahydrofurfuryl alcohol solo-,-

tion to recover separately. the alcohol and water components for recycling in the system.

' ILLIAM G. KNOX.

GEORGE L. DENISTON,

REFERENCES CITED The following references are of record in the file of this patent: f 

1. THE METHOD OF REMOVING COLOR BODIES FROM SOLUTIONS OF LOW GRADE ROSIN WHICH COMPRISES, MIXING A SOLUTION OF ROSIN IN A WATER IMMISCIBLE PRIMARY SOLVENT WITH A SECONDARY WATER MISCIBLE SOLVENT HAVING SOLVENT POWER FOR THE COLOR BODIES TO FORM A HOMOGENEOUS SOLUTION, SEGREGATING A PRIMARY SOLVENT RICH PHASE AND A SECONDARY SOLVENT RICH PHASE, SPRINGING SAID SECONDARY SOLVENT FROM EACH PHASE BY ADDITION OF WATER THERETO, SEGREGATING A PALE ROSIN SOLUTION, A DARK ROSIN SOLUTION AND A SPRINGING AGENT-SECONDARY SOLVENT SOLUTION, AND RECOVERING THE SOLVENTS AND SPRINGING AGENT FOR REUSE IN THE SYSTEM. 